Sean Barron: Never followed the #F1Testing, external this intently before. Feel like Columbo trying to work out who is showing their true hand

Simon Newby: But are @McLarenF1, external going to give us a last minute "just one more thing" moment? 

Image source, Rex Features

Image source, Getty Images

F1 journalist Dan Knutson in Barcelona:  Mercedes is not concentrating on all-out lap times as Valtteri Bottas has been doing longer runs including some 14-lap stints, plus in and out laps. With just over an hour to go, he was fifth fastest on the timing screens while team-mate Lewis Hamilton was fourth behind a Williams, a Red Bull and a Ferrari.

Just how much better will the Mercedes W08 be at the first race in Australia 19 days from now? 

“I think it will just start coming together,” Hamilton said. “At the moment there are bits coming in, and the car is improving overall. But I am told that by Melbourne we will have the best car to date – all around great parts; we will have a better understanding of the set-up, and know where we need to put the car to make it comfortable.” 

How close does Hamilton think Ferrari is to Mercedes? 

“I have no idea,” he said. “When we left here last week, it looked like Ferrari were our closest rivals. Or were very close, and then all of a sudden today Red Bull looks quite quick. So think these next days are going to be really, really interesting, and then [again] when we get to Australia.”

A cracking effort from Nico Hulkenberg as he does a 1:21.989 on softs to leap up to ninth. So far so good after Renault ran into a problem this morning that led to an engine change.

Speaking of engine change, McLaren are also going well now. Stoffel Vandoorne is up to 50 laps for the day.

Sebastian Vettel and Felipe Massa are very much locked in a battle to see who can finish with the most laps today. 

Massa has just moved ahead of Vettel on 123. The latter, who pitted after lap 122, heads back out.

Jim I Am: Are @HassF1Team, external just doing lots of laps because @KevinMagnussen, external can't stop? Or have they fixed last years breaking issues?  

Think you might be onto something, Jim. I haven't seen him stop yet.

Image source, Getty Images

F1 journalist Dan Knutson in Barcelona: Lewis Hamilton completed just 49 laps this morning before handing the Mercedes over to team-mate Valtteri Bottas for the afternoon.

“It is a work in progress,” Hamilton said when he and his dog Roscoe showed up to talk to the TV crews. “This morning I did not get a huge amount of laps in. Compared to last week the track was not feeling as great this morning. We are just trying to get in as much running as we can.”

Hamilton stopped running about 30 minutes before the lunch break.

“We had some damage to the floor,” he said, “and so we had to make sure that Valtteri could get lots of testing in in the afternoon. We think the afternoon will be better. I sacrificed a little bit of my time to make sure that Valtteri had a better time.”

Valtteri Bottas is creeping up on his team-mate Lewis Hamilton's time from this morning. The Finn has just done a 1:21.313, eight tenths slower than Hamilton. Bottas is currently fifth, with Hamilton fourth.

Sebastian Vettel (Ferrari) - 112

Felipe Massa (Williams) - 100

Esteban Ocon (Force India) - 88

Kevin Magnussen (Haas) - 68

Daniel Ricciardo (Red Bull) - 64

Daniil Kvyat (Toro Rosso) - 49

Stoffel Vandoorne (McLaren) - 43

Valtteri Bottas (Mercedes) - 30  

Marcus Ericsson (Sauber) - 20  

Nico Hulkenberg (Renault) - 14

Felipe Massa is 100 not out. He joins Sebastian Vettel in nailing 100 laps today. With 90 minutes to go, there's plenty of time for them to add significantly to that.

Massa, by the way, stays in the car tomorrow morning with Lance Stroll, who had a torrid time last week, taking over in the afternoon and then having the Williams to himself on Thursday.

Image source, Getty Images

F1 journalist Dan Knutson in Barcelona: McLaren’s racing director Eric Boullier talked with reporters after the mechanics had to change the engine on Stoffel Vandoorne’s car that had an electrical problem this morning.

He was asked how worried and concerned he was now heading into the start of the season given this latest round of reliability woes.

“Not very much concerned yet, I would say,” he replied. “Obviously we got hurt in our job to understand the car, develop the car, validate some parts, but the process today is more about generating data as much as we can. And feed the machine back in Woking and make sure the correlation is working with CFD or wind tunnel or anything else because everything else is based on our simulation.

“So on this part obviously we would like more laps because we want to test more parts, but the few we have done were good. The correlation was good, so we can now build on predictions. This part is okay, so not concerned yet. For the rest, obviously I leave the decisions in the hands of Honda to make sure they investigate properly, they address it properly, and we have to rely on our partner that they will do it, and we believe that they will do it.”

Andrew Benson
Chief F1 writer

As Stoffel Vandoorne returns to the track after Honda managed to fit a replacement engine to the McLaren, it might be instructive to recap what’s happened to Honda and its engines as far as we know so far in pre-season testing. Bear with me, because it might make your head hurt.

We know there have been three failures followed by changes. But we also know that Honda changed the engine (or power-unit) overnight Monday into Tuesday last week and Wednesday into Thursday, because they have told us they did. 

They say they have used “a mixture of PUs so some PUs have been used on multiple days”. So let’s break it down.

Test one, day one: McLaren start testing last week with a new engine. They discover an oil-tank problem. The engine is changed and the replacement runs to the end of the day. The engine is changed again overnight, Honda has confirmed to BBC Sport.

Test one, day two: There is an engine failure in the morning and the engine is changed. It runs to the end of the day. Honda have not said whether it was changed overnight.

Test one, day three: The engine that starts the day runs reliably throughout. The engine is changed overnight, Honda has confirmed to BBC Sport.

Test one, day four: The engine that starts the day runs reliably throughout. 

Test two, day one: Honda say the engine that started the second test was not new. It suffers electrical problems. Engine change.

Honda are being very cagey about how many engines have been used in total - they say they don’t disclose the number of engines used in testing. They have said it is “not six” engines. But have not clarified whether that means it is only five.

Phew. Follow that? Either way, it doesn’t look good, does it?

Right, I'm going to have splash my face with cold water because after a lull that was almost nap-inducing it's all happening now.

Stoffel Vandoorne is back out for McLaren and is cracking straight on with some solid laps, his first of which is 1:22.816s, a touch slower than his best effort from this morning.

Meanwhile, Sebastian Vettel improves again as a 1:19.906 puts him to within 0.006s of Daniel Ricciardo in P2. Vetel's time has come on slower tyres than Ricciardo's did.

James Harris: As well as the lap time update Gary, could you include an 'engine change' time leaderboard? McLaren should surely be top of that!   

Good news, McLaren fans! They are back on the track. 

Stoffel Vandoorne has just been out for an installation lap but is back in the pits now.

Here's hoping it is not long before they are back out again.

Kevin Magnussen has been quietly totting up the laps for Haas. He's got 63 under his belt, with his fastest lap a 1:21.676. He's just gone back out on the circuit with supersofts bolted on, so could improve on the time that is currently seventh quickest.

Big season ahead for the K-Mag. He moved from Renault to Haas for this year with some reports, external suggesting this is his last chance to stay in F1.

1) Felipe Massa (Williams) 1:19.726

2) Daniel Ricciardo (Red Bull) 1:19.900

3) Sebastian Vettel (Ferrari) 1:19.986

4) Lewis Hamilton (Mercedes) 1:20.456

5) Esteban Ocon (Force India) 1:21.347

6) Valtteri Bottas (Mercedes) 1:21.375

7) Kevin Magnussen (Haas) 1:21.676

8) Daniil Kvyat (Toro Rosso) 1:21.965

 9) Stoffel Vandoorne (McLaren) 1:22.698

10) Pascal Wehrlein (Sauber) 1:23.336

11) Marcus Ericsson (Sauber) 1:23.630

12) Nico Hulkenberg (Renault) 1:24.028

13) Jolyon Palmer (Renault) 1:24.790

Loving the little flames!

For anyone not familiar with the reference, see 13:02 GMT entry.

Sebastian Vettel joins Felipe Massa and Daniel Ricciardo in posting a sub-1:20s time. He does 1:19.986 but stays third, two tenths off Massa's time.

Meanwhile, Valtteri Bottas is up to sixth following a 1:21.375.